1. Field of the Invention
Electro-mechanical key arrangements are well known in the art, and heretofore have taken the form of a mechanical key type device which is physically shaped, or formed, so that when it is inserted into the lock receptacle it will physically close a plurality of electrical lines (i.e., make a plurality of contacts). The closing of these electrical lines will provide an electrical logic circuit which will provide electrical power to an electro-mechanical device, such as a solenoid, to open a lock. Normally the bolt on the lock is spring-loaded and will return to the locked position when the key is removed or the electrical energy is terminated for some other reason.
As illustrative of prior locking systems which have been proposed reference may be had to the U.S. Pat. Nos. to Watson, 1,695,518; Block, 2,006,624; Durant, 3,148,525; Taylor, 2,473,664; Rose, 3,347,072; Christensen, 3,355,631; Swannick, 3,411,046; Kramasz, et al., 3,415,087; Isserstedt, 3,654,522, and Bostrom, 3,686,659.
The above described mechanisms, or systems, have been satisfactory up to a point but have been unsatisfactory if there was a power failure, or if the lock had to be changed to thwart the use of a key by some unauthorized person, or if the user wanted an alarm sounded when a wrong key was inserted.